In my U.S. Pat. No. 4,090,061, I described and claimed an electrical air heater which combines a motor driven blower that is surrounded by an 5 electrical resistance heating element consisting of vane like strips which serve both to heat the air and also act as guide vanes to help and redirect the air from the blower.
It was determined through recent testing that the air flow efficiency as claimed in my U.S. Pat. No. 4,090,061 is not realized due to the fact that the air emanating from the heating element is at a high velocity and at a relatively shallow angle to the tangent.
The high air velocities, are responsible for pressure losses, and also generate a noise level that would be undesirable for certain domestic application.
In one embodiment of my above mentioned patent the blower heater combination is surrounded by a blower housing which would alleviate the problem mentioned above by providing a gradual diffusion of the high velocity. The heated air would thus be delivered out of a defined outlet which is very usable in some applications such as a hair dryer, but not so desirable in other applications, as would be discussed herewith.
It has become apparent that there exist many applications where a concentrated stream of heated air would not be required or even desired; instead a low-velocity heated air volume would be more appropriate. In such applications the concentric arrangement of the blower and heating element are still of a great advantage, due to the improved heat transfer properties of the turbulent air flow and the uniformity of the air flow along the entire heating element cylinder. In order to further enhance the aerodynamic efficiency of the system a concentric molded ring of guide-vanes are placed around the heating element. The guide vanes further diffuse the heated air thereby reducing the tangential component of the air velocity converting it to static pressure, according to Bernoulli's theorem.
Applications where a low velocity and therefore silent heated air flow would be of great benefit would include space-heaters, foot warmers, towel drying appliances, flat garment dryers etc. Further on in this specification some such applications would be discussed to illustrate the advantages of the system.